package com.lazy.rabbit.demo.rpc;

import com.rabbitmq.client.ConnectionFactory;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.QueueingConsumer;
import com.rabbitmq.client.AMQP.BasicProperties;
  
public class RPCServer {

    private static final String RPC_QUEUE_NAME = "rpc_queue";

    private static int fib(int n){
        if(n == 0)
            return 0;
        if(n == 1)
            return 1;
        return fib(n - 1) + fib(n - 2);
    }

    public static void main(String[] argv){
        Connection connection = null;
        Channel channel = null;
        try{
            ConnectionFactory factory = new ConnectionFactory();
            factory.setHost("localhost");

            connection = factory.newConnection();
            channel = connection.createChannel();

            channel.queueDeclare(RPC_QUEUE_NAME, false, false, false, null);

            channel.basicQos(1);

            QueueingConsumer consumer = new QueueingConsumer(channel);
            channel.basicConsume(RPC_QUEUE_NAME, false, consumer);

            System.out.println(" [x] Awaiting RPC requests");

            while(true){
                String response = null;

                QueueingConsumer.Delivery delivery = consumer.nextDelivery();

                BasicProperties props = delivery.getProperties();
                BasicProperties replyProps = new BasicProperties.Builder().correlationId(props.getCorrelationId()).build();

                try{
                    String message = new String(delivery.getBody(), "UTF-8");
                    int n = Integer.parseInt(message);

                    System.out.println(" [.] fib(" + message + ")");
                    response = "" + fib(n);
                }catch(Exception e){
                    System.out.println(" [.] " + e.toString());
                    response = "";
                }finally{
                    channel.basicPublish("", props.getReplyTo(), replyProps, response.getBytes("UTF-8"));

                    channel.basicAck(delivery.getEnvelope().getDeliveryTag(), false);
                }
            }
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            if(connection != null){
                try{
                    connection.close();
                }catch(Exception ignore){
                }
            }
        }
    }
}
